Decabromodiphenylethane is a time-proven flame retardant for use in many flammable macromolecular materials, e.g. thermoplastics, thermosets, cellulosic materials and back coating applications of very high quality.
Governmental regulating agencies tend to be moving away from partially brominated analogs and more towards perbrominated compounds as evidenced by the recent EU RoHS (Restriction on Hazardous Substances) directive (2002/95/EC) relating in part to partially brominated diphenyl oxides. Even with the exemption of decabromodiphenyl oxide from RoHS per 2005/717/EC, the regulations have not been clear enough in terms of the acceptable nonabromodiphenyl oxide content in electrical and electronic products. Some end users therefore find it uncomfortable using the commercial decabromodiphenyl oxide in which significant amounts of nonabromodiphenyl oxide exists as impurity. In order to meet the strictest interpretation of RoHS by the end users, a high assay version of decabromodiphenyl oxide is being marketed by Albemarle Corporation. In view of the confusion concerning the presence of small quantities of lower brominated impurities in the flame retardant products, there is thus a need in the marketplace for very high assay perbrominated flame retardants.
Decabromodiphenylethane is presently sold as a powder derived from the bromination of 1,2-diphenylethane. Among prior processes for effecting such bromination are the bromination processes described in U.S. Pat. Nos. 6,518,468; 6,958,423; 6,603,049; 6,768,033; and 6,974,887. Decabromodiphenylethane has been commercially produced by the assignee of this application for many years using a standard process. Each batch of product was analyzed by a GC procedure. A review of the GC analyses indicated that the average bromine content of over 4000 batches of decabromodiphenylethane product was 97.57 area percent with a 3-sigma precision of ±1.4 area percent. The equipment used for those analyses did not include a present-day data collection system that can electronically fine tune the peaks of the chromatogram. In some cases, the analysis of the product from a given run provided assays of decabromodiphenylethane in the region of about 99 area percent and above, and in some other cases significantly lower GC assays were obtained. The reasons for this variance cannot be established from the information available.
Gas chromatographic analysis of commercial decabromodiphenylethane products available in the marketplace from other manufacturers have, in some cases, also given assays of a decabromodiphenylethane product as high as about 99.6 area percent. In other cases, GC analyses of commercial decabromodiphenylethane products available in the marketplace have indicated the presence of much lower amounts of decabromodiphenylethane in the product. Information on the method by which such high assay products were produced and the purification procedures used, if any, is not generally available to the public.
From at least the standpoint of providing environmentally-friendly process technology, it would be highly desirable if commercially feasible processes could be found that would produce on a consistent basis a decabromodiphenylethane product that comprises at least about 99.50 GC area percent of decabromodiphenylethane (Br10DPE), with the balance consisting essentially of nonabromodiphenylethane (Br9DPE). Such product is hereinafter often referred to in the specification and claims hereof as “high assay decabromodiphenylethane product”. Moreover, this high assay decabromodiphenylethane product is a “reaction-derived” product which term as used herein including the claims, means that the composition of the product is reaction determined and not the result of use of downstream purification techniques, such as recrystallization or chromatography, or like procedures that can affect the chemical composition of the product. Adding water or an aqueous base such as sodium hydroxide to the reaction mixture to inactivate the catalyst, and washing away of non-chemically bound impurities by use of aqueous washes such as with water or dilute aqueous bases are not excluded by the term “reaction-derived”. In other words, the products are directly produced in the synthesis process without use of any subsequent procedure to remove or that removes nonabromodiphenylethane from decabromodiphenylethane.